1. Field of the Invention
The present invention relates to grafted silicone polymers and to products made therewith, especially personal care products including cosmetics.
2. Related Background Art
Cosmetics are widely used for cleaning, care, protection and appearance enhancement of skin, hair and nails. Skin cosmetics prepared in the forms of gels, emulsions or creams are used for prevention and amelioration of rough skin that may result when skin is washed or exposed to water in the workplace. Such skin cosmetics adjust the skin moisture balance by supplying water, moisturizing agents and oils to the skin, thus having a moistening and softening effect.
Housewives, physicians and barbers are among those that perform cleaning or otherwise work with water and are at risk of suffering from roughened skin. Skin roughening may progress before moisture, moisturizing agents and oils can be supplied, often producing inflammation in more serious cases. When this occurs, it is the usual practice to apply a hand cream that includes petrolatum or a moisturizing agent as non-volatile components. However, since hand creams wash away during cleaning or working with water and tend to stick to objects that are contacted, they may require frequent re-application to maintain the therapeutic benefits and usually do not have long-term durability.
Skin-protecting cosmetics that form water-resistant coatings on the skin prior to some user activity are useful by helping avoids loss of moisture, natural moisturizing factors and lipids experienced during subsequent cleaning or working with water, thus helping to prevent skin roughening. Such cosmetics usually contain silicone oils or film-forming acrylic polymers or silicone polymers to provide water repellency.
Skin-protecting cosmetics employing organic silicone resins are disclosed, for example, in Japanese Examined Patent Publication No. 6-15448 and Japanese Patent Publication No. 2539190.
Other skin-protecting cosmetics include sunscreen cosmetics that protect skin by blocking ultraviolet ray components in sunlight, namely UVA (320 nm-400 nm) and UVB (290 nm-320 nm), and suntan lotions that help produce uniformly tanned skin without causing UVB-induced erythema. Especially when used under the strong ultraviolet rays of summer, it is important for sunscreen cosmetics to form water-resistant coatings in order to fix the ingredients so that they do not escape into seawater or through sweat. Sunscreen cosmetics employing an organic silicone resin are disclosed, for example, in Japanese Examined Patent Publication No. 6-72085.
Hair care products utilize conditioning agents that include cationic surfactants or amino-modified silicones, but these can produce a sticky feel as well as allergic reactions. Although proteins are sometimes used as conditioning agents, their adhesion is poor and they are readily washed off by water.
Makeup cosmetics that are applied onto skin, hair and nails, and especially the skin and eyelashes, should form water-resistant and sebum-resistant coatings to prevent makeup deterioration or wear off due to sweat, tears and sebum. Improving the adhesion of makeup cosmetics to skin by dispersing pigments or inorganic powders in oil bases has been attempted, but this tends to produce a sticky feel. Japanese Patent Publication No. 3552741 discloses an eye makeup cosmetic that contains an organic silicone resin and an acrylic-silicone polymer obtained by radical polymerization of a radically polymerizable monomer composed mainly of a (meth)acrylic acid ester, with a dimethylpolysiloxane compound having a radically polymerizable group at one end of the molecular chain.
Japanese Patent Publication No. 2700816 also discloses application of an acrylic-silicone polymer, likewise obtained by radical polymerization of a radically polymerizable monomer (composed mainly of a (meth)acrylic acid ester with a dimethylpolysiloxane compound having a radically polymerizable group at one end of the molecular chain), for cosmetics. The basic structure of these polymers is composed of a silicone compound side chain grafted onto an acrylic polymer main chain.
Japanese Patent Publication No. 2939309 discloses a process for production of a vinyl-silicone polymer obtained by solution polymerization of a mercapto-modified silicone and a radically polymerizable vinyl monomer, as a film-forming agent with asserted superior adhesion and long-lasting functionability, as well as its application as a release coating for pressure-sensitive adhesives. This type of polymer has a structure with vinyl side chains grafted onto the silicone polymer main chain. The mercapto-modified silicone polymer is used as a chain transfer agent, and its reactivity is high. Because mercapto-modified silicone polymers can be prepared by several methods and their compositional ratios and molecular weights can be easily altered, a large variety of mercapto-modified silicone polymers are readily available. Japanese Laid-Open Patent Application No. 7-508027 and Japanese Laid-Open Patent Application No. 10-512233 disclose cosmetics employing vinyl-silicone polymers obtained by solution polymerization of mercapto-modified silicones with radically polymerizable vinyl monomers.
There has long been a need for 1) a polymer which has sufficiently high solubility in non-skin-irritating volatile solvents to thus ensure sufficient freedom of formulation, and which when used as a cosmetic component is able to form coatings with a minimal sticky feel on the skin coupled with satisfactory water and sebum resistance, and 2) cosmetics containing such polymers.